Preston James "PJ" Carpenter is an agent with the CIA.
This highly experienced operative is a man in his early 40s based on the fact that he joined the Agency nearly 20 years before the first recorded adventure, going on the likelihood of that employment starting when he was around 22.
We are given a concise introduction to Carpenter early in the first recorded adventure:
"Preston James Carpenter, PJ to his family and close friends, joined the Central Intelligence Agency nineteen years earlier, right after graduating with honors from Northwestern University. The agency's recruiters had been particularly drawn to his overseas experience and language skills. He majored in Middle East and North Africa studies and minored in linguistics. During a year at the American University of Beirut in fulfillment of a program requirement, Carpenter honed his fluency in Arabic, Farsi, and French. Their concerns about potential behavioral problems, however, had almost derailed Carpenter's chances."
Those concerns start with his alcohol-driven abusive step-father who took his anger out on Carpenter and his mother, once beating her for the apparently serious crime of not having enough beer in the house. When Carpenter was 14, his mother died and after the funeral, he used his fists to let the man know he had had enough abuse. Several incidents of violence would be noted over the next few years but in each instance, the "authorities determined [his] actions had been equally justified".
Carpenter joined the Agency before 9/11. When the Towers fell and the CIA sent operatives into Afghanistan to try and locate al Qaeda, he was one of those agents and he spent considerable time in-country.
It was then that he made an interesting career move. Rather than accept a desk job back at Langley, he applied for transfer to the paramilitary section. While it was normal to take military personnel from the special operations ranks and train them to be operatives, Carpenter went the other route and trained to be the very best spec-ops agent possible.
The move fulfilled his inner desire to be on the side of justice and he was given that chance in assignments over the next two decades in over 40 countries.